It will be good if there is a column or indicator in jira issue search result list to indicate if I am already watcher for the issue.

One typical things we do is periodically review newly incoming jira issues and for those I am interested in , add myself as watcher.
So wheneve the issue subject is interesting to me, I will drilldown the the issue detail page, and review in detail and add myself as watcher, but often the issue I might have watched before during prior review, so have a column or indicator on the jira result list for this would be helpful.

To make it a more powerful generic feature, maybe you can allow the user to add a custom dynamic column on the result list to refer to a jira expression,